The global war on terror has presented the military with new challenges. One such challenge is the redesign of combat vehicles to safely carry personnel and or cargo. One of the most important requirements for a combat vehicle's protection is counter mine design. These new mine/IED protected vehicles and armored fighting vehicles are designed for anti-personnel or larger anti-tank mines, armor penetrating and self-forged fragmented mines as well as improvised explosive devices (IEDs). To provide maximum protection new vehicles use special lower frame V shapes to deflect a mine blast with increased armor and clear armor windows for blast and bullet defense. Engines and transmissions are also housed within armor. The only outside openings that can be safely opened are the firing ports located in the doors and side panels. This added ballistic protection of the engine, transmission, and crew compartment has increased the cabin thermal load and mass thereby substantially increasing the load on the heating, cooling, and ventilation of the crew compartment.
Present tactical and non tactical vehicle heating and air conditioning systems use two independent engine driven heat transfer fluid systems in order to heat or cool the interior or cabin environment of a vehicle. Typically, in order to heat the interior, heated engine coolant is circulated from the engine through a liquid-to-air type heat exchanger located in or near the interior of the vehicle. In order to cool the interior, an engine driven compressor is typically used to compress a refrigerant. The condensed refrigerant is then allowed to pass through a refrigerant-to-air type heat exchanger (e.g. an evaporator coil) also located in or near the interior. In addition, present vehicle air ventilation systems may draw filtered or unfiltered air from the ambient environment.
There are several disadvantages in using such engine driven independent systems for the heating and cooling of a vehicle interior. First, using separate heating and cooling systems requires the use of twice as many fluid conduits and heat exchangers. In other words these independent systems typically include one set of fluid conduits and an interior heat exchanger for heating and one set of fluid conduits and an interior heat exchanger for cooling. Having two sets of fluid lines and heat exchangers not only incurs additional expense in the manufacture of the vehicle, but also contributes to the overall vehicle weight and consumption of valuable cabin space. This is particularly the case in larger transport vehicles that have multiple heat exchangers in the interior. For example, extended cab vehicles, large passenger vans, and military tactical vehicles typically include two in-dash heat exchangers, two mid-cabin heat exchangers, and two rear cabin heat exchangers. The two heat exchangers are normally packaged together with a common blower in order to effectively and adequately heat or cool the entire interior. In some applications a large single interior heat exchanger is used while a high CFM blower forces the treated air via ductwork to multiple locations throughout the interior. This ductwork consumes additional interior cabin space, requires the use of insulation, and must be sufficiently rigid so that it does not collapse or bend during the loading or unloading of personnel and cargo. It can be seen that cost, weight, and space are all important concerns.
Yet another disadvantage of the conventional heating, cooling, ventilation system is that the engine of the vehicle must be running in order to produce heat. Furthermore, there is usually some delay in the production of heat under cold weather starting conditions. Under these conditions, the engine must first warm the engine coolant to an operating temperature that is high enough (usually 150-210 deg F.) to produce heated interior airflow from a coolant water to air heat exchanger. This delay in heat production can be inconvenient for the driver and passengers in the cabin. Besides heating the vehicle interior, the front windshield may also need to be heated or defrosted before the vehicle can be driven. In such cases, waiting for the engine to sufficiently warm to defrost the front windshield can increase the time needed before the vehicle can be driven
Yet another disadvantage of a conventional heating, cooling, ventilation system is that the engine must be running to provide the mechanical rotational energy for air conditioning compressor and engine water pump rotation. During times of loitering or silent watch, personnel may remain inside the vehicle for safety and for protection against the outdoor environment. When loitering or under silent watch, it is generally preferred that the engine be shut off. This loss of engine rotational energy for air conditioning and engine water pump operation stops interior heating, cooling and ventilation. During cold weather operation the interior can become as cold as the surrounding ambient. Cold weather clothing can help retain body heat but wearing such clothing is both cumbersome and restrictive. Therefore, lack of heat when the engine is off can also be a problem.
In cold weather conditions, the interior vehicle temperature will rarely if ever be lower than the exterior ambient temperature. On the other hand, during hot weather conditions, the interior vehicle temperature can significantly exceed exterior ambient temperatures. The exterior color of the vehicle, solar radiation entering through the windows of the vehicle, and additional heat load from the surrounding ground (radiating under and around the vehicle) all contribute to the temperature rise inside the vehicle. In many instances personnel are unable to remove protective clothing to aid in reducing body temperature. As a result, the interior vehicle temperature can become extreme within minutes. Prolonged exposure to elevated temperatures can cause physical stress that ultimately impairs the ability of personnel to perform.
Yet another disadvantage of present conventional heating, cooling, ventilation systems is that fresh air filtration systems provide limited protection from harmful gasses and biological contaminants. In many cases carbon based filters and particulate filters are undersized for ease of integration and to keep consumer costs low, and thus only limited protection is provided. In addition, airflow density and velocity through the filters is not managed thus producing off gassing and reducing overall capacity.
Yet another disadvantage of present conventional heating, cooling, and ventilation systems, particularly for military vehicles, is the use of externally mounted Nuclear, Biological, and Chemical (NBC) filtration systems. These filtration systems are intended to slightly over pressurize the vehicle interior. Current state of the art NBC filtration systems are self-contained and mounted outside of the vehicle. This approach exposes the ventilation over pressurization system to heat and cold, increasing the load on the vehicle heating and cooling system. In addition, an exterior mounted system is outside of standard vehicle protective armor and may require additional shielding or armor for protection. This further contributes to vehicle weight, time required to service the system, and mounting complexity. Another disadvantage of an exterior mounted system is that it provides additional surfaces where weapons such as hand grenades could become stuck or lodged.
Yet another disadvantage of the conventional heating, cooling, ventilation system is that vehicle NBC ventilation over pressurization systems regulate the interior pressure of the vehicle by increasing or decreasing the over pressurizing air flow. These systems do not monitor the density or velocity of the air moving through an NBC filter system. As such, the particulate and vapor adsorbing ability of the filter system can be greatly reduced.
Yet another disadvantage of the conventional heating, cooling, ventilation system is the introduction into the vehicle interior of external filtered over pressurization air. Current systems introduce the filtered airflow directly into the interior or into the recirculation airflow of the heater/air conditioner. The method of mixing the ambient filtered air flow before passing the ambient air through a heat exchanger is less efficient than introducing the ambient air directly to the heat exchanger.
Yet another disadvantage of the conventional heating, cooling, and ventilation system is the lack of airflow control for use with a military personnel cooling vest. During cooling vest operation, air flow from the heating, cooling, and ventilation system is used to provide heat transfer from a cooling vest heat exchanger to the fluid inside of the vest. The lack of a conditioned airflow control can impede the efficient operation of the cooling vest. As with a high interior vehicle temperature, insufficient vest cooling can cause physical stress that ultimately impairs the ability of personnel to perform.
For at least these reasons there is a need to provide a heating, cooling and ventilation system for a vehicle interior that is compact, effective, and concealed by protective armor (for military vehicles) while providing occupant comfort and safety during both engine on and off conditions. The present invention therefore relates to an improved design for a heating, cooling and ventilation system for a vehicle interior.